Substrate holder which is self-adjusting for substrate deformation

ABSTRACT

A wafer chuck is designed to allow the substrate to thermally deform during charged particle beam lithography. The wafer chuck includes a compliant layer disposed over an chuck body. During lithography processing the wafer is electrostatically held in contact with a flexible compliant layer and the wafer is exposed to the charged particle beam resulting in thermal deformation of the wafer. The compliant layer deforms with the substrate and allows the wafer to deform in a predictable manner.

FIELD OF THE INVENTION

The present invention relates generally to wafer processing systems forsemiconductor fabrication, and more specifically to a wafer holder forlithography systems, and other wafer processing steps.

BACKGROUND OF THE INVENTION

As the degree of circuit integration has increased, the feature sizes ofIC's have dramatically decreased. To support future semiconductorfabrication requirements, lithography systems using charged particlebeams, such as electron beams or ion beams, have been developed toovercome feature size limitations of traditional optical systems. Incharged particle beam projection lithography systems, portions of a maskare exposed to a charged particle beam to project an image of the maskonto a substrate. Several new charged particle beam lithography systemshave been developed to extend lithography capabilities to sub-0.15micron feature size levels. One such system is a microcolumn electronbeam system developed by IBM. This system uses a large number ofminiature electron beam writers in a phased array to project mask imageson the order of 0.1 micron wafer geometries. A similar electron beamprojection lithography system is known as PREVAIL® also developed byIBM.

Another electron beam lithography system is a SCALPEL® developed by AT&TBell Laboratories; SCALPEL, stands for “Scattering with AngularLimitation in Projection Electron-beam Lithography” and is a registeredtrademark of AT&T Bell Laboratories of Murray Hill, N.J. The SCALPELlithography system exposes a photomask to high-energy electrons toproject an image of the mask onto a substrate, coated with an energysensitive material or resist. During semiconductor fabrication multiplelayers are deposited on the substrate and several layers may be exposedto the patterned high-energy electrons.

Proper alignment of the mask image with preexisting features on thewafer during lithography processing is critical because many patterenedlayers must be aligned within specific tolerances to produce functionalintegrated circuits. The alignment tolerance or alignment budget of aprojected pattern is proportional to the critical dimension (CD) of thecircuit. A typically alignment tolerance or alignment budget is CD/3.During processing, the wafer is held on a chuck within the processingchamber typically by vacuum or electrostatic force. To ensure accuratepositional registration, points on the wafer are interrogated ormeasured by the lithography tool alignment systems to automaticallydetermine the locations of the preexisting features. This enables thenext pattern level to be accurately positioned.

In conventional optical 248 nm, 193 nm wavelength UV, deep-UV,extreme-UV and electron beam lithography, energy density typicallybetween about 10-25 mJ/cm² is applied to the wafer. If the energyapplied to the wafer during conventional lithography processing is lowand the wafer temperature rise is small (less than 0.1° C.), thermalexpansion is small compared to the tolerances required at the featuresizes that can be printed with such tools. In lithography systems wherethe wafer temperature rise is less then 0.1° C., alignment correctiondue to thermal expansion is typically not required.

In wafer processing systems were thermal expansion needs to becontrolled, thermalization of the wafer is a commonly used practice.Thermalization maintains a wafer at a constant temperature by passingconstant temperature air over the surface during processing. Becausethermalization requires the circulation of air, it is not compatiblewith vacuum chamber systems.

Some semiconductor and lithography processes, including SCALPEL, exposea smaller area of the wafers to substantially more energy which resultsin thermal distortion of the wafer. The exposure of the wafer to a highenergy particle beam having an energy density of more than 1.0 Joule/cm²creates local heating at the area of incidence and can increase thelocal temperature from approximately 1° to 50° centigrade. As theparticle beam traverses the wafer and energy is absorbed duringlithography processing hot spots on the wafer are produced. These hotspots result in localized thermal expansion of the wafer. In lithographysystems which project images with critical dimensions less than 0.15 μm,wafer temperature variations as low as 0.1° to 1° C. can produce enoughthermal deformation to cause misalignment.

In lithography systems that expose the wafer to higher energy levels,the wafer temperature may be stabilized by control mechanisms which coolthe wafer and reduce thermal expansion. Some wafer chucks have beendesigned to prevent wafer heating by circulating a fluid under the waferto cool the wafer during processing. Wafer cooling chucks have been usedprimarily in systems which expose the entire wafer to plasma or ionbeams during processing. Multiple zone wafer cooling chucks have alsobeen developed which monitor the temperature of various areas of thewafer and independently adjust the cooling of each area to maintain thedesired uniform water temperature. In general, however, multiple-zonewafer cooling chucks cannot prevent thermal deformation of wafers inhigh energy particle beam lithography systems because the energyabsorbed by the wafer can not be removed quickly enough by conventionalconvection heat transfer mechanisms to prevent local heating of thewafer and thermal expansion. Also, because the high energy particle beamis quickly scanned across the substrate, the independent cooling zonesof the present wafer cooling chucks may not be able to regulate auniform temperature across the entire wafer to prevent thermaldeformation.

The magnitude of thermal deformation of the substrate during lithographyis proportional to the change in temperature of the substrate. Becauseparticle beam lithography systems may only heat a small area and scanthe wafer, the thermal deformation of the wafer varies throughout thelithography process and is not uniform. Thermal deformation due toheating during lithography processing can result in 10 to 100 nm ofwafer movement.

As discussed, during lithography processing the substrate is generallyheld in contact with a chuck by a vacuum or electrostatic force. Becausethe wafer is held on a chuck by force, significant friction force canoppose any relative motion between the wafer and chuck including thermaldeformation of the wafer. The friction force is dependent on thesubstrate material, the chuck material, the clamping force and thecondition or roughness of the surfaces in contact.

During lithographic processing, the substrate is exposed to a highenergy particle beam which produces a substantial amount of heat at thepoint of incidence. The thermal expansion force of the heated substrateis opposed by the friction forces between the substrate and chuck whichprevents the wafer from expanding until the thermal expansion forceexceeds the friction force. When the thermal expansion force exceeds thefriction force the substrate quickly expands and is prevented fromexpanding again until the thermal expansion force again exceeds thefriction force this type of affect is sometimes referred to as“stick-slip” motion. The relationship of the thermal expansion force andfriction force causes the substrate to thermally deform in anincremental manner.

Similarly, as the substrate cools the thermal contraction force buildsuntil the deformation force exceeds the friction force. Again, when thecontraction force exceeds the friction force the substrate moves quicklyand is prevented from contracting again until the thermal contractionforce exceeds the friction force. Like the thermal expansion, thesubstrate contracts in an incremental manner. Stick-slip is a knownproblem in the fields of high energy lithography systems, monochromatorsand frequency stabilized lasers.

Stick-slip causes the thermal expansion of the substrate to beunpredictable and makes alignment of the substrate during processingextremely difficult. Alignment computer systems may be used tocompensate for the thermal deformation of a substrate, however currentalignment computer systems can not accurately determine the substrateposition during thermal deformation having stick-slip motion.

SUMMARY OF THE INVENTION

The present invention relates to a wafer chuck which has a compliantlayer interface in contact with the substrate that allows the wafer tothermally deform without stick-slip during lithographic processing. Thecompliant layer is in direct contact with the substrate and issufficiently flexible to allow the substrate to deform without anyrelative movement between the substrate and compliant layer duringlithography processing. Because the complaint layer deforms with thesubstrate during localized heating there is no relative movement betweenthe substrate and compliant layer during lithography processing.

A microprocessor system utilizes the processing conditions and physicalcharacteristics of the substrate to predict and measure the thermaldeformation of the substrate throughout lithography processing. Bypredicting and measuring the thermal deformation of the substrate, themicroprocessor can adjust the incident electron beams with chargedparticle beam deflectors to compensate for the wafer's thermaldeformation. As a result of the microprocessor's compensation forthermal deformation, the projected images are accurately aligned duringlithography processing.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings, in which likereferences indicate similar elements, and in which:

FIG. 1 is a cross sectional illustration of a charged particle beamlithography system;

FIG. 2 a is a cross sectional illustration of an embodiment of theinventive electrostatic chuck;

FIG. 2 b is a cross sectional illustration of an alternate embodiment ofthe inventive electrostatic chuck; and

FIG. 3 is the thermal motion of the substrate versus time duringlithographic processing.

DETAILED DESCRIPTION OF THE INVENTION

A system for securely holding a wafer during lithographic processing isdescribed. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be evident, however, toone of ordinary skill in the art, that the present invention may bepracticed without these specific details. The description of preferredembodiments is not intended to limit the scope of the claims appendedhereto.

During lithographic processing, charged particles or radiation aredirected through a mask to project an image of portions of the mask ontoa substrate, such as a silicon wafer having an energy sensitive or photoresist layer. Typical charged particle beam lithography systems useelectron beam or ion beam projection systems to fabricate a wafer usingan image mask. In one embodiment of the present invention, the waferholding system is implemented in a SCALPEL (Scattering with AngularLimitation in Projection Electron-beam Lithography) system.

As is well known, in a SCALPEL system, high-energy electrons areprojected through a mask. Various types of masks are suitable for usewith SCALPEL systems. A typical SCALPEL mask has two types of regionsthat scatter electrons more or less strongly. The electrons pass throughthe mask to project an image of the mask onto the substrate. The mask isessentially transparent to energized electrons (typically 100 keV) ofthe electron beam; however, the difference in electron scatteringcharacteristics between the less strongly scattering and more stronglyscattering regions, when differentiated by an aperture, providessufficient contrast at the wafer plane for lithographic purposes. Withreference to FIG. 1, system 110 represents the electron optical systemof a SCALPEL lithography system that includes embodiments of the presentinvention. The mask stage 106, chuck 112 and imaging column 110 areenclosed within a process chamber 120. For a SCALPEL system, the processchamber 120 is generally maintained at a sub-atmospheric environment andthus may also be referred to as a vacuum chamber. The optical systemincludes an electron source 102, which is typically implemented as anelectron gun. Electron source 102 projects electrons 103 through anillumination column in an illumination chamber 104 to mask stage 106.Mask stage 106 holds a mask 108 that includes strongly scatteringregions and less strongly scattering regions. The electron beams passthrough the mask 108 and an imaging (or projection) column 110 to formfocused electron beams 105 that are projected onto a wafer 114 held bychuck 112. Imaging column 110 also includes a back-focal plane aperturethat blocks strongly scattered electrons and allows less stronglyscattered electrons to pass through to the wafer 114.

With reference to FIG. 2 a, an embodiment of the present invention isillustrated in more detail. Electrostatic chuck 112 comprises a pedestal210 containing an electrode 224 and a compliant layer 222 which is incontact with the wafer 114 during lithography processing. With referenceto FIG. 2 b, an alternative embodiment of the present invention isillustrated. Electrostatic chuck 112 comprises a pedestal 210 and anoverlying compliant layer 222 which is in contact with the wafer 114during lithography processing.

The electrode 224 is made from any suitable electrically conductivematerial, some examples being, copper, nickel, chromium, aluminum, iron,and mixtures or alloys thereof. The electrode 124 may have a thicknessfrom about 1 μm to 1,000 μm. The chuck 110 is typically configured tohold wafer 114 perpendicular to an imaging column 110 axis whichprojects patterned images onto the wafer 114. The chuck 112 exerts anattractive force which holds the wafer 114 onto the chuck 112.

In one embodiment of the present invention, the compliant layer 222 ismade of a flexible polymer such as but not limited to fluorosilicones,polyamides, polyimides, polyketones, polyetherketones, polysulfones,polycarbonates, polystyrenes, polyurethanes, nylons, polyvinylchlorides,polypropylenes, polyetherketones, polyethersulfones, polyethyleneterephtlialate, fluoroethaylene propylene copolymers, cellulose,triacetates, silicones and rubbers. Other suitable compliant layermaterials having low particulate and low metal content are alsoavailable.

The compliant layer may also include filler materials for increasing thethermal conductivity and/or resistance to corrosion or abrasion.Preferably, the filler materials is a powder with an average particlesize significantly smaller than the thickness of the compliant layer.The particle size of the filler material is preferably less than about 1μm. The filler is dispersed in the polymer film in a volumetric ratiofrom about 10% to 80%, and more typically from about 20% to 50%. Fillerssuch as diamond, alumina, zirconium boride, boron nitride and aluminumnitride are preferred because these materials have high thermalconductivity, good insulative properties and can withstand hightemperatures.

The complaint layer may be formed on the chuck by spraying, molding,spinning or attaching in any other appropriate manner. The compliantlayer may have a thickness from about 1 μm to 10 μm. The compliant layeralso prevents the flow of electrons between the electrode and the wafer.Optimally, the shape and size of the compliant layer corresponds to theshape and size of the wafer to provide a good heat transfer path to coolthe wafer during processing. Alternatively, the compliant layer may havea different shape and size than the wafer.

Multiple compliant layers having different characteristics may also beformed on the chuck. For example, to improve the life of the compliantlayer, a harder material may be used on the exposed surfaces to improveabrasion resistance and an underlying elastic material may be used tomaintain the flexible characteristics. In another example, the primerlayer may be used between the electrode and the main compliant layer toimprove the adhesion between the electrode and the main compliant layer.

In one embodiment of the present invention, the compliant layer shouldexhibit the following characteristics: a flexible surface (Shorehardness scale A between 25 and 75), good electric insulation, gooddielectric properties (dielectric constant between 1.0 and 3.0),moderate thermal conductivity, sufficient elasticity, low outgassing ina vacuum, low lift-off force, low hysteresis to electrostaticchucking-dechucking and no shedding of particles during waferprocessing.

As discussed previously, a problem associated with thermal expansion ofwafers, is that wafers thermally deform in a stick-slip manner due tothe friction force between the wafer and the chuck as illustrated inFIG. 3. The present invention eliminates the stick-slip problem byproviding a flexible layer that deforms with the wafer duringlithography processing. Specifically, because there is no relativemovement between the wafer and the upper surface of the compliant layer,there are no friction forces opposing the thermal deformation forces ofthe wafer which produces stick-slip. By processing wafers on a chuckhaving a compliant layer the thermal deformation of the wafer is smooth.Although friction forces do not oppose the wafer's thermal deformation,the elasticity of the compliant layer may oppose the wafer expansionforces and assist the wafer contraction forces. The compliant layer actslike a two dimensional spring, stretching during wafer expansion andreturning to its normal shape during wafer contraction.

Referring to FIG. 3, the solid line 304 represents the motion of thewafer during processing on a chuck that does not have a compliant layer.The horizontal sections represent the “stick” periods when the wafer isnot moving. The vertical sections represent the “slip” periods when thewafer is sliding relative to the chuck.

The dashed line 302 represents the thermal deformation of a wafermounted on the inventive chuck during charged particle beam lithographyprocessing. The sideways movement of the wafer is smooth because thereis no relative movement between the wafer and the upper surface of thecompliant layer in contact with the wafer. The compliant layerdeformation curve is effected by the elastic properties of the complaintlayer. As discussed, the compliant layer acts as a two dimensionalspring resisting wafer expansion and accelerating wafer contraction. Thecompliant layer deformation curve may change with use due to thehysteresis effect from repetitive deformation.

Because the thermal deformation characteristics of the chuck withcompliant layer are predictable and repeatable, wafers mounted on theinventive chuck may be more accurately exposed to patterned chargedparticles or radiation. Specifically, because the thermal deformation ofthe wafer is free from stick-slip, the exact position of the wafer canbe determined and the projected mask image can be adjusted to compensatefor the thermal deformation of the wafer.

During processing the wafer is placed against two rigid edge referencepoints and may be held on the chuck with an attractive clamping forcegreater than 5 N. Because the wafer is in contact with the flexiblecompliant layer and the compliant layer deforms with to the wafer,friction forces do not act upon the wafer during lithography processing.Because there is no sliding between the wafer and compliant layer, metaland polymer particles are not shed from the wafer or complaint layer andthe chamber contamination is minimized. After processing the clampingforce is removed and the lift off force required to separate the waferfrom the inventive chuck may be less than 5 N. The compliant layer doesnot leave residue on the wafer when the wafer is removed from the chuck.

It is well known that the lift off force after processing can be veryhigh when a smooth wafer surface is in contact with a smooth waferchuck. In order to reduce this lift off force the exposed surface of achuck is often roughened. Dimpling is one method of roughening the chucksurface and reducing the lift off force. Similarly fine grooves (1100per cm) may be formed on the chuck surface to roughen the surface.

During lithography processing, the upper surface of the compliant layerexpands with the wafer while the bottom surface remains, Fixed to theelectrode resulting in sideways deformation and shear stress within thecomplaint layer. In one embodiment, the compliant layer is capable ofshear deformation between 2% to 10% relative to the compliant layerthickness. During charged particle beam lithography the thermaldeformation of the wafer is typically less than 0.1 μm. A 0.1 μmdeformation of a 1.0 μm thick compliant layer produces 10% sheardeformation. Preferably the compliant layer is between 1.0 and 3.0 μmthick.

The wafer plane deformation of the compliant layer may result incontraction of the complaint layer thickness because the volume of thecompliant layer may be constant. A sideways expansion in the range of0.1 μm or less may result in a decrease of 1 to 20 nm in the compliantlayer thickness. Because the wafer is mounted on the compliant layer,the distance between the wafer and the optical system changes. Theprojected mask image quality should not be affected by the small (1 to20 nm) wafer movement which is well Within the depth of focus of theoptical system.

Because the thermal deformation is smooth and free from stick-slip, theexpansion and contraction of the wafer mounted on the inventive chuckcan be accurately determined for a given wafer temperature. Further, thewafer position can be predicted throughout lithography processing withthe inventive chuck because the wafer temperature is carefully monitoredand/or calculated during charged particle beam lithography processing.

In SCALPEL, or sub-field scanning lithography systems, if the exactposition of the wafer during processing is known, deflection units canredirect the beam to compensate for movement of the wafer duringprocessing. This compensatory charged particle beam deflection resultsin accurate positioning of the mask image on the wafer. Thus, it iscritical for the lithography system to know the exact position of thewafer at all times during processing. The inventive chuck improveslithography processing because stick-slip is removed and the waferposition can be accurately determined during lithographic processing.

In an embodiment, a computer is programmed to predict the wafer positionbased upon a “look-forward predictive model”. In the semiconductormanufacturing art, the fabrication processes are carefully controlledand accurately repeated during manufacturing. Because the wafers areprocessed in a carefully controlled repetitive manner each wafer willhave identical thermal deformation. By knowing how wafers thermallydeform during processing, the lithography system is configured to directthe charged particle beam to anticipate the thermal deformation of thewafer.

In another embodiment of the present invention, lithography processingincludes on-wafer registration alignment. In SCALPEL lithographysystems, on-wafer registration aliment is achieved by scanning the imageof a mark on the mask over a corresponding mark on the wafer. Abackscattered electron signal, which represents a convolution of the twomarks, is then detected and analyzed. The lithography system computeranalyzes the backscattered electron signal and automatically correctsdetected errors in rotation, magnification and distortion. Thelithography system computer determines the required system settings tocorrect the alignment error and corrects the control signals to the maskstage, wafer stage and imaging column.

In one embodiment of the present invention temperature sensors and/ortemperature monitors determine the localized temperatures across thewafer during the lithography process. The localized wafer temperatureinformation is forwarded to a computer which calculates the waferposition and controls the deflection units to redirecting chargedparticle beams to compensate for the thermal deformation of the wafer.

As discussed, the present invention allows the wafer to expand andcontract without sliding between the wafer and the compliant layer.Because there is no sliding there is no particle generation. Thisability to avoid particle generation is beneficial not only tolithography systems, but any other wafer processing apparatus thatrequires a high level of cleanliness. Thus the present invention is animprovement to any type of semiconductor processing system in which thewafer thermally deforms. These applications are not limited to waferholders fixed within a processing chamber, for example wafers aretypically transported between processing chambers with a robotic arm.Because wafers are often heated during processing, the wafer may thermaldeform while being transported between processing chambers. By using acompliant layer with the wafer holder on a robotic arm would reduceparticle generation within the semiconductor processing equipment.

Although specific embodiments of the present invention have beendiscussed in relation to a SCALPEL lithography system, it will beappreciated by those of ordinary skill in the art that embodiments ofthe present invention may also be used in other types of systems. Suchsystems may include: deposition, etch, passivation, thermal processing,robotic arm, micro-column electron beam systems, ion beam projectionsystems, and similar types of lithography systems. In these cases, thechuck with a compliant layer is used in the same manner described abovein relation to the SCALPEL system.

In the foregoing, a wafer holding system for use with charged particlebeam lithography system has been described. Although the presentinvention has been described with reference to specific exemplaryembodiments, it will be evident that various modifications and changesmay be made to these embodiments without departing from the broaderspirit and scope of the invention as set forth in the claims.Accordingly, the specification and drawings are to be regarded in anillustrative rather than a restrictive sense.

1-40. (canceled)
 41. A substrate holder for retaining a substrate withina processing chamber comprising: an electrode; and one or more layerscovering a portion of said substrate holder which contacts a substrate,where at least one of said layers is compliant, so that said portion ofsaid substrate holder which contacts said substrate deforms with saidsubstrate, avoiding relative movement between said substrate and saidcontacted portion of said substrate holder, when there is thermaldeformation of said substrate surface during processing, and whereinsaid compliant layer can withstand at least 10% shear stress withoutexceeding a yield strength of said compliant layer material.
 42. Thesubstrate holder of claim 41, wherein said compliant layer is anelectrical insulator having a dielectric constant between 1 and
 3. 43.The substrate holder of claim 41, wherein the electrode comprises atleast one conductive material selected from the group consisting of:copper, nickel, chromium, aluminum, iron, and mixtures or alloysthereof.
 44. The substrate holder of claim 41, wherein said compliantlayer comprises an insulative material selected from the groupconsisting of: fluorosilicones, polyamides, polyimides, polyketones,polyetherketones, polysulfones, polycarbonates, polystyrenes,polyurethanes, nylons, polyvinylchlorides, polypropylenes,polyethersulfones, polyethylene terephthalate, fluoroethylene propylenecopolymers, cellulose, triacetates, silicones and rubbers, andcombinations thereof.
 45. The substrate holder of claim 41, wherein saidcompliant layer is between 1 μm and 10 μm thick.
 46. An apparatus forprojecting patterned charged particles onto a substrate comprising: aprocessing chamber; a charged particle source for generating a chargedparticle beam that impinges on the substrate; and an electrostatic chuckcomprising an electrode and one or more layers covering a portion of asubstrate holder which contacts a substrate, where at least one of thelayers is compliant, so that the portion of the substrate holder whichcontacts the substrate deforms with the substrate, avoiding relativemovement between the substrate and the contacted portion of thesubstrate holder, when there is thermal deformation of the substratesurface during processing, and wherein said compliant layer canwithstand at least 10% shear stress without exceeding a yield strengthof said compliant layer material.
 47. The apparatus of claim 46, furthercomprising: a computer for calculating an estimated charged particlebeam deflection to compensate for the actual deformation of thesubstrate caused by the exposure of the substrate to the chargedparticle beam, wherein the computer generates a deflection signalcorresponding to the calculated deflection; and a beam deflector fordeflecting the charged particle beam in response to the deflectionsignal from the computer.
 48. The apparatus of claim 46, wherein thecompliant layer is an electrical insulator having a dielectric constantbetween 1 and
 3. 49. The apparatus of claim 46, wherein the electrodecomprises a conductive material selected from the group consisting of:copper, nickel, chromium, aluminum, iron, and mixtures thereof.
 50. Theapparatus of claim 46, wherein the compliant layer comprises aninsulative material selected from the group consisting of:fluorosilicones, polyamides, polyimides, polyketones, polyetherketones,polysulfones, polycarbonates, polystyrenes, polyurethanes, nylons,polyvinylchlorides, polypropylenes, polyethersulfones, polyethyleneterephthalate, fluoroethylene propylene copolymers, cellulose,triacetates, silicones and rubbers, and combinations thereof.
 51. Theapparatus of claim 46, further comprising: a lithography mask positionedbetween the charged particle source and the substrate; and an electronsensor disposed within the processing chamber for detectingbackscattered electrons emanating from the substrate.
 52. The apparatusof claim 46, further comprising a substrate temperature sensor formeasuring the temperature of the substrate during processing and forsending a signal corresponding to the measured substrate temperature tothe computer.
 53. The apparatus of claim 46, wherein the compliant layeris between 1 μm and 10 μm thick.
 54. The apparatus of claim 48, whereinlocalized heating of the substrate due to exposure to the charged beamis between 1° C. and 50° C.
 55. A method for patterning a photoresistlayer on a substrate comprising the steps of: forming a photoresistlayer on the substrate; positioning the substrate on an electrostaticchuck having one or more layers covering a portion of the chuck whichcontacts the substrate, where at least one of the layers is compliant,so that the portion of the electrostatic chuck which contacts thesubstrate deforms with the substrate, avoiding relative movement betweenthe substrate and the contacted portion of the electrostatic chuck, whenthere is thermal deformation of the substrate during processing, andwherein said compliant layer can withstand at least 10% shear stresswithout exceeding a yield strength of said compliant layer material; andexposing portions of the photoresist layer on the substrate to a chargedparticle beam.
 56. The method of claim 55, further comprising the steps:computing an estimated deformation of the substrate caused by exposureof the substrate to the charged particle beam; and deflecting theparticle beam in response to the estimated deformation.
 57. The methodof claim 55, further comprising: using a charged particle beam to scan afirst mark on a photo lithography mask onto a second mark on saidsubstrate; detecting backscattered electrons from said scanning step;determining the position of the substrate using the detectedbackscattered electrons; and deflecting the charged particle beam inresponse to the measured position of the substrate.
 58. The method ofclaim 55, wherein the compliant layer is an electrical insulator havinga dielectric constant between 1 and
 3. 59. The method of claim 55,wherein the compliant layer comprises an insulative material selectedfrom the group consisting of: fluorosilicones, polyamides, polyimides,polyketones, polyetherketones, polysulfones, polycarbonates,polystyrenes, polyurethanes, nylons, polyvinylchlorides, polypropylenes,polyethersulfones, polyethylene terephthalate, fluoroethylene propylenecopolymers, cellulose, triacetates, silicones and rubbers, andcombinations thereof.
 60. The method of claim 59, wherein the exposingstep is performed using a SCALPEL lithography system.
 61. Anelectrostatic chuck for use in substrate processing, the chuck having anelectrode covered by an electrically insulative layer for receiving thesubstrate, wherein the improvement comprises: an electrically insulativelayer which is elastic, in a manner such that the portion of theelectrostatic chuck which contacts the substrate deforms with thesubstrate, avoiding relative movement between the substrate and thecontacted portion of the electrostatic chuck, when there is thermaldeformation of the substrate during processing, and can withstand atleast 10% shear stress without exceeding the material yield strength.62. The electrostatic chuck of claim 61, wherein the electricallyinsulative layer comprises an insulative material selected from thegroup consisting of: fluorosilicones, polyamides, polyimides,polyketones, polyetherketones, polysulfones, polycarbonates,polystyrenes, polyurethanes, nylons, polyvinylchlorides, polypropylenes,polyethersulfones, polyethylene terephthalate, fluoroethylene propylenecopolymers, cellulose, triacetates, silicones and rubbers, andcombinations thereof.
 63. A method for holding a substrate on a chuckhaving an electrode and one or more layers covering a portion of thechuck which contacts the substrate, the method comprising the steps of:selecting the layers so that at least one of the layers covering theportion of the chuck which contacts the substrate is compliant so thatthe portion of the chuck which contacts the substrate deforms with thesubstrate, avoiding relative movement between the substrate and thecontacted portion of the chuck, when there is thermal deformation of thesubstrate during processing, and wherein said compliant layer canwithstand at least 10% shear stress without exceeding a yield strengthof said compliant layer material; placing the substrate on one of thelayers of the chuck; and energizing the electrode.
 64. The method ofclaim 63, wherein the compliant layer is an electrical insulator havinga dielectric constant between 1 and
 3. 65. The method of claim 63,wherein the electrode comprises at least one conductive materialselected from the group consisting of: copper, nickel, chromium,aluminum, iron, and mixtures or alloys thereof.
 66. The method of claim63, wherein the compliant layer comprises an insulative materialselected from the group consisting of: fluorosilicones, polyamides,polyimides, polyketones, polyetherketones, polysulfones, polycarbonates,polystyrenes, polyurethanes, nylons, polyvinylchlorides, polypropylenes,polyethersulfones, polyethylene terephthalate, fluoroethylene propylenecopolymers, cellulose, triacetates, silicones and rubbers, andcombinations thereof.
 67. The method of claim 63, wherein the compliantlayer is between 1 μm and 10 μm thick.
 68. An apparatus for handling asubstrate for use in semiconductor processing comprising: a substrateholder; and one or more layers covering a portion of the substrateholder which contacts the substrate, where at least one of the layers iscompliant, so that the portion of the substrate holder which contactsthe substrate deforms with the substrate, avoiding relative movementbetween the substrate and the contacted portion of the substrate holder,when there is thermal deformation of the substrate during processing,and wherein said compliant layer can withstand at least 10% shear stresswithout exceeding a yield strength of said compliant layer material. 69.The apparatus of claim 68, wherein the compliant layer comprises aninsulative material selected from the group consisting of:fluorosilicones, polyamides, polyimides, polyketones, polyetherketones,polysulfones, polycarbonates, polystyrenes, polyurethanes, nylons,polyvinylchlorides, polypropylenes, polyethersulfones, polyethyleneterephthalate, fluoroethylene propylene copolymers, cellulose,triacetates, silicones and rubbers, and combinations thereof.
 70. Theapparatus of claim 68, wherein the compliant layer is between 1 μm and10 μm thick.